Mechanical vibrating system



BEST AVAEABIE COPY Aug- 25, 1942- w. NIEDERMEIER MECHANICAL VIBRATING SYSTEM Filed March 14, '1939 l l l I u I Patented Aug. 25, 1942 menswear. vranarmc SYSTEM Willy Niedermeier, Berlin, Germany,

assignor to C. Lorenz Aktiengesellschaft, Berlin-Tempe]- hol', Germany, a company Application March 14, 1939, Serial No. 261,855 In Germany April 13, 1938 2 Claims.

The present invention relates to mechanical vibratory systems and has for its object to provide means in order to suppress harmful noises set up by such system during operation.

Mechanical vibratory apparatuses, such as current chopper devices, buzzers, electromagnetic self-interrupters and the like, are frequently employed for various purposes in the electrotechnics and it is a matter of fact that the noise set up by the mechanically vibrating member or members of such devices in many cases becomes rather disagreeable. It is therefore proposed according to the main feature of this invention to provide means which reliably suppress the annoying noise resulting from the operation of the vibrating member of the above identified systems.

When dealing with the problem of noise suppression, two components must be considered, viz. the sound wave propagation in the space and the sound conduction through bodies which on account of their natural properties are caused to vibratein resonance with vibrations imparted thereto. The elimination of these two components would reliably cause the suppression of harmful noises.

This problem is solved according to my invention by placing a mechanical vibratory apparatus in a container capable of sound wave absorption or suppression and by so arranging this container in a further container that substantially no sound can be conducted from the first to the second container.

The invention will be more readily understood from the following description, taken in conjunction with the accompanying drawing, the single figure of which shows one embodiment of my invention.

The reference C in this drawing denotes any optional type of mechanical vibratory apparatus which may be assumed to set up disagreeable noises during operation. Such apparatus is placed in a cup-shaped container B which is completelyclosed in any suitable manner by a cover B in the shape of a disc or plate having a central downwardly extendedstem b integral with or attached to the disc or plate B. Both the container B and the cover B are made of a sound damping or sound absorbing material, such as rubber, cork, felt or similar materials for eliminating sound wave propagation to the exterior of this container.

The mechanical sound conduction is obviated by means of the second container A, A comprising a cup-shaped member A and a discor plateshaped cover A having a central downwardly extending projection a. The interior of this projection is made hollow for the opposite or upper side of the disc to receive the stem b in such manner that there is an airgap between the closure plates or discs A and B. The size of the outer container A, A is so chosen with respect to that of the inner container B, B that an airgap exists between the entire inner surface of the outer container and the outer surface of said inner container in order to completely avoid eventually residual or not completely damped sound waves from the inner container to be conducted to the outer one. The container B carries at its outer boundary small extensions D which maintain the sound wave absorbing member in its proper position relative to the outer container without ofiering substantial mechanical coupling between the two containers. The conductors leading to the mechanical vibratory apparatus C are preferably carried through the stem b and the wall of the projection (11.

What is claimed is:

1. An arrangement for reducing sound emanating from a sound emitting apparatus, comprising an inner enclosure of a sound dampening material completely enveloping said apparatus, a stem protruding from said enclosure, an outer enclosure enveloping said inner enclosure, and an air space extending substantially all around said inner enclosure and between said inner and outer enclosure, said outer enclosure having a recess to receive said stem.

2. Apparatus according to claim 1 in which the outer surface of said inner enclosure is provided with contacting members oi small contacting area to contact with the inner surface of the outer enclosure.

' WILLY NIEDERMEIIIR. 

